Figure 2.
The top panel shows the effects of pretreatment with three doses of i.m. methamphetamine or saline on responding for 3 μg/kg/injection i.v. methamphetamine or food. Each curve is the mean of 4–5 monkeys (*p < 0.05 from saline pretreatment). The bottom panel shows the effects of pretreatment with saline or with either 0.3 or 1.0 mg/kg i.m. methamphetamine on responding for various self-administration doses of i.v. methamphetamine or saline (S). Each curve is the mean of five monkeys. *p < 0.05 from saline self-administration following saline pretreatment, #p < 0.05 from saline pretreatment at the comparable i.v. methamphetamine dose.